Recently, in order to solve the problems of network backup and resource sharing, IU FLEX concept is introduced into third generation partnership projects (3GPP) protocol. In other words, a universal terrestrial radio access network (UTRAN) supports an intra domain connection routing function from one radio access network (RAN) node to a plurality of core network (CN) nodes, and allows the RAN node to route the information to different CN nodes in a corresponding circuit switched (CS) domain or a packet switched (PS) domain.
POOL AREA concept is introduced into the IU FLEX technique, and one pool area is a collection of one or more RAN node service areas. The pool area is composed of a plurality of CN nodes equally, and the CN nodes share the communication amount with one another in the pool area. A mobile switching centre (MSC) collection in the pool area is referred to as an MSC pool. A serving GPRS supporting node (SGSN) collection in the pool area is referred to as an SGSN pool.
A user equipment (UE) may roam in the pool area without changing the serving CN node. One pool area may serve several parallel CN nodes, and the pool area may separately configure the CS domain and the PS domain. From the perspective of the RAN, the pool area includes all the location areas/routing areas (LA/RA) of the one or more RNCs served by a group of parallel CN nodes, and the group of CN nodes may serve the LA/RA outside the pool area and may also serve other pool areas. The group of CN nodes may be the corresponding MSC pool or SGSN pool. A plurality of CN nodes in one area pool may realize the load balance, and the serving coverage provided by the plurality of CN nodes is much larger than the service area provided by a single CN node, which thus reduces node update, handoff, and relocation among the CNs, thereby reducing the update flow of a home location register (HLR).
All the CNs in the IU FLEX networking belong to the same operator. In addition, multi-operator CN (MOCN) characteristic is introduced into the 3GPP, the MOCN networking has the CNs of a plurality of operators. The CN of one operator may be the POOL of one CN, CS is the MSC pool, and the PS is the SGSN pool.
It is known that one RNC is connected to the nodes of a plurality of CNs of the same operator (PLMN) simultaneously in the IU FLEX networking manner, and one RNC is connected to the nodes of a plurality of CNs of different operators (PLMN) simultaneously in the MOCN networking manner, in which each operator may have a plurality of CNs.
FIG. 1 is a networking diagram of a typical MOCN and IU FLEX.
Three operators are involved, namely, a CN of operator A, a CN of operator B, and a CN of operator C. The CN refers to the MSC or the SGSN. If the CN of the operator A is the MSC, a collection of MSC-A1, MSC-A2, and MSC-A3 is referred to as the MSC pool. If the CN of the operator A is the SGSN, a collection of SGSN-A1, SGSN-A2, and SGSN-A3 is referred to as the SGSN pool.
The load of the CN is balanced, the load reallocation after the failure is restored is realized, or the load reallocation after the certain MSC or SGSN exits from or adds to the service is realized through a service load reallocation solution by utilizing the networking structure. The process is realized by cooperating the CN and the RNC.
The process of the load reallocation of the CS domain is shown in FIG. 2.
It is assumed that the MSC1 is shunted, and O&M respectively set a shunting flag on the RNC and the MSC1.
1. The UE under the MSC1 initiates an initial direct transfer message, the RNC resolves a network resource identifier (NRI) value in an intra domain non-access stratum (NAS) node selector (IDNNS) after receiving the message, wherein the NAS selects the MSC1 through the IDNNS CN selecting algorithm, and the RNC sends a location registration message in the initial direct transfer message to the MSC1.
2. The MSC1 receives the location registration message, determines that the UE is the user of this MSC, and performs a subsequent location registration flow.
3. The CN initiates a flow relating to the security function.
4. The MSC1 determines that this MSC has a load shunting flag, the location registration message includes a reallocated temporary mobile subscriber identity (TMSI) and unbroadcasted location area information (LAI), and the TMSI includes a null network resource identifier (NULL-NRI).
5. The UE sends a TMSI reallocation complete message to the MSC1.
6/7. A flow of releasing the location registration of this time is initiated.
8. The location registration flow is reinitiated after the UE receives a location registration accept message and finds that the LAI is unbroadcasted. After receiving the initial direct transfer message, the RNC resolves the NRI value (should be NULL-NRI) in the IDNNS, and the RNC selects one MSC without the load shunting flag in the MSC pool by using the NULL-NRI.
9. The RNC sends the location registration message in the initial direct transfer message to the selected MSC.
10. The MSC initiates a subsequent normal location registration flow after receiving the location registration flow.
The process of the load reallocation of the PS domain is shown in FIG. 3.
It is assumed that an SGSN1 is shunted, and O&M respectively set the shunting flag on the RNC and the SGSN1.
1. A UE under the SGSN1 initiates an initial direct transfer message, and after receiving the initial direct transfer message, the RNC resolves an NRI value in an IDNNS, selects the SGSN1 through the IDNNS CN selecting algorithm, and sends a routing area update (RAU) request message in the initial direct transfer message to the SGSN1.
2. The SGSN1 receives the RAU Request message, determines that the UE is the user of this MSC, and performs a subsequent RAU flow.
3. The CN initiates a flow relating to the security function.
4. The SGSN1 determines that this SGSN has a load shunting flag, and the RAU accept message includes a reallocated packet-TMSI (P-TMSI) and unbroadcasted routing area identity (RAI). A periodic RA update timer is set to a smaller value, and the TMSI includes an NULL-NRI.
5. The UE sends an RAU complete message to the SGSN1.
6/7. A flow of releasing the location registration of this time is initiated.
8. The UE reinitiates the RAU flow after the Periodic RA Update Timer reaches the set time, the RNC resolves the NRI value (should be NULL-NRI) in the IDNNS after receiving the initial direct transfer message, and the RNC selects one SGSN without the load shunting flag in the SGSN pool by using the NULL-NRI.
9. The RNC sends the RAU request message in the initial direct transfer message to the selected SGSN.
10. The SGSN continues the subsequent RAU flow after receiving the RAU request message.
It is known from the above flow that the process of realizing the load reallocation of the CN must be realized through the cooperation of the CN and the RNC in the solution of the prior art, thus having a high complexity. Furthermore, the shunting process is finished by performing the location registration flow twice for the CS domain, and the shunting process is finished by performing the RAU flow twice for the PS domain. Therefore, the performance of the existing network is seriously affected.